Harbin city officials temporarily restored water supplies to allow residents to stock up.

Residents rushed to shops to stock up on food and water in a city where winter temperatures regularly drop below minus 20 Celsius. People crowded the airport and railway stations to leave the area, a witness said.

The provincial government said the 80 km (50 mile) stretch of polluted river water would reach Harbin's water supply inlet later on Thursday and flow past the city itself on Saturday.

"We hope citizens can take time to hoard as much water as possible," an executive from the Harbin water company was quoted as saying by China's Xinhua news agency.

The provincial government has told Harbin residents to stay away from the river to avoid possible exposure to airborne contaminants coming off the water, Xinhua said.

The State Environmental Protection Administration said the polluted water contained nearly 30 times more than normal levels of chemicals with benzene, an industrial solvent and component of petrol.

"GRIM ENVIRONMENTAL SITUATION"

Chinese Premier Wen Jiabao chaired a government meeting on pollution problems in the country.

"Our country's environmental situation remains grim," the State Council was quoted as saying by Xinhua.

"As the economy has expanded, waste of resources and energy has continued growing, and the pressures on environmental protection are increasingly heavy."

By late on Wednesday, feelings among Harbin residents seemed to be shifting from panic to anxious resignation and anger. Most shops and restaurants remained open, although business was generally slow.

Wang Qiang, a rural migrant who works in a Harbin bathhouse, said his employer had put him on unpaid holiday.

"We have to pay for drinking water ourselves. It's not cheap, but I can afford it. But I hope this won't go on for too long," he said.

Provincial governor Zhang Zuoji promised to be the first person to drink tap water when supplies were restored.

"After four days, I'll have the first drop," he said.

Chinese people usually boil tap water before drinking it, even when pollution is not an issue.

A deputy governor of neighbouring Jilin province, site of the petrochemical plant, visited Harbin to apologise for the pollution spill, the Harbin Daily newspaper said.

"A lot of people here blame Jilin for not acting sooner after the explosion," said Harbin resident Zhou Qicai. "There were at least several days between the explosion and when they issued any warnings for downstream."

Russia's environmental protection agency said on Wednesday it was worried the pollution could affect drinking water supplies in its Khabarovsk region, which the Songhua enters several hundred kilometres downstream from Harbin.

Russian Natural Resources Minister Yuri Trutnev said all steps would be taken to ensure there was no health risk, the RIA Novosti news agency reported.

"But so as to make sure these measures are effective, we need more information from the Chinese. We need to more accurately know the make-up of the pollutants," he said.